This invention relates to rectifiers used in alternators of automobiles, and more particularly, this invention relates to a rectifier having an improved heat dissipation and cooling ability for use with Internal Alternator Regulator (IAR) style alternators.
Most automotive systems use the automobile engine to drive an alternator via a belt transmission or similar driving transmission that rotates a drive shaft of the alternator, which includes a rotor coil where a magnetic field is generated. A stator is positioned about the rotor coil and positioned in the magnetic field. The stator windings are wound about stator laminations in typically a three-phase configuration. As the engine drives the belt transmission, the alternator drive shaft rotates and an electric current is induced in the stator windings.
In these types of automotive alternator systems, the alternating current induced in the stator windings is converted to a direct current by a rectifier that is electrically connected to the stator windings. In many prior art alternator designs, including an IAR style alternator, an internal or integrated alternator/regulator is positioned in the alternator housing, such as disclosed in U.S. Pat. Nos. 6,252,320; 6,140,722; 5,821,674; and 6,107,710.
The ""722 and ""320 patents disclose a prior art rectifier having a thin, negative heat sink plate and a positive connector plate positioned on the negative heat sink plate. A housing cover extends over the negative heat sink plate. Negative diodes are positioned on the negative heat sink plate. Positive diodes are positioned on the positive connector plate. The cover carries various terminals and connects to a B+ post secured typically by soldering to the positive connector plate.
An improvement over that type of prior art rectifier design is disclosed in the ""722 and ""320 patents by using first and second diode mounting plates that define negative and positive heat sinks. Openings are formed in each plate and dimensioned to receive a diode in a press fit relationship. A connector housing includes a connector box having a recess to receive a wiring harness, a B+ post, and other components used for AC power rectification.
Other rectifier designs, such as disclosed in the ""674 patent, also include a negative and positive heat sink plate. Some prior art rectifier designs use more substantial negative and positive heat sink plates having greater mass to enable heat transfer. A gasket separates the positive and negative heat sink plates. Some of these rectifiers use multiple heat sink plates and separate components for both the positive and negative heat sink plates. Other prior art rectifiers use complicated lead integument connectors or a connector for connecting rectifier diode circuits and other circuit components to a wiring harness.
Many of these prior art rectifiers do not provide sufficient thermal mass for allowing heat transfer from the diodes and through the rectifier, and thus, the diodes often fail in operation. Also, the separate negative and positive heat sink plates in some designs require additional manufacturing steps that increase assembly time and costs. The use of a B+ post for battery connection may also require a separate soldering step to secure the B+ post onto a heat sink and another solder connection for a lateral terminal connector to the post. This also adds increased cost and assembly steps.
Some prior art rectifiers increase the size of the negative heat sink plate to enhance heat conduction from the diodes, through the heat sink plate, and to the alternator body on which the rectifier is mounted. Usually, a dielectric is plasma sprayed on the heat sink plate. An example is aluminum oxide. It is applied onto the negative heat sink plate. A layer of copper or other metallic material is applied onto the aluminum oxide to form an electrically insulated layer on which positive diodes can be placed. Various terminals interconnect the positive and negative diodes in a typical bridge rectifier arrangement, which is then interconnected to a connector housing that allows a wiring harness to be connected thereto.
Although the larger heat sink plates supply some additional cooling capacity, the positive diodes do not transfer heat adequately in that type of system.
It is therefore an object of the present invention to provide a rectifier that overcomes the drawbacks of the prior art as noted above.
It is yet another object of the present invention to provide a rectifier for an internal alternator regulator (IAR) style alternator that has improved heat sink capability and can be formed as a one-piece construction.
The rectifier of the present invention is preferably used for an IAR style alternator and includes an integrally formed rectifier body having a ground engaging surface that mounts within the alternator and is grounded through the automotive grounding system. A diode receiving cavity is formed opposite the ground engaging surface. By ground engaging surface, it is meant that the rectifier body is grounded via the grounding system of the automobile, such as through the alternator body or other means. A diode receiving cavity is formed opposite the ground engaging surface. A plurality of negative diodes are secured within the diode receiving cavity and grounded thereto. An insulated conductive substrate is positioned in the diode receiving cavity and has a conductive surface that is insulated from the rectifier body and the negative diodes secured thereto. A plurality of positive diodes are secured on the insulated conductive substrate. A terminal connector interconnects the negative and positive diodes in an electrical rectifying configuration, such as a bridge configuration.
In one aspect of the present invention, the insulated conductive substrate is formed as a dielectric layer having a circuit layer positioned thereon on which the positive diodes are secured. A metal base layer can be secured on the dielectric layer opposite the circuit layer. In yet another aspect of the present invention, the insulated conductive substrate is formed as a fiberglass reinforced bond ply material having a metal layer on both sides. Each metal layer comprises a copper layer in one preferred aspect of the present invention.
A capacitor is secured within the diode receiving cavity and operatively connected to the negative diodes and positive diodes. An epoxy filler is disposed within the diode receiving cavity and covers the diodes to protect and insulate same. Cooling fins are formed on the rectifier body to aid in heat transfer.
In yet another aspect of the present invention, a connector housing connects to the terminal connectors and has a connection for connecting to a wiring harness. A terminal connector is secured to the insulated conductive substrate and has a terminal that connects to a wiring harness. This terminal connector can include dual terminals that connect to a wiring harness.
In yet another aspect of the present invention, the rectifier body is formed from cast aluminum, but can be formed from other metallic and electrically conductive materials as suggested by those skilled in the art.
A method of forming a rectifier for an IAR style alternator is also disclosed. In the method of the present invention as a non-limiting example, the steps include the step of securing an insulative conductive substrate within a diode receiving cavity of an integrally formed rectifier body having a ground engaging surface opposite the diode receiving cavity. The ground engaging surface mounts within an alternator and is grounded through an automotive grounding system. The leads are positive and negative diodes and inserted within a terminal connector that interconnects same. The interconnected positive and negative diodes are inserted within the diode receiving cavity such that negative diodes engage the rectifier body and are grounded thereto. Positive diodes engage the insulated conductive substrate.
In yet another method aspect of the present invention, the method includes the step of securing the negative and positive electrodes within the diode receiving cavity by applying solder paste to the rectifier body within the diode receiving cavity and onto the insulated conductive substrate and securing the negative and positive diodes thereto. A capacitor can be secured within the diode receiving cavity such that the capacitor is operatively connected to the negative and positive diodes.
The method also includes the step of filling the diode receiving cavity with an epoxy filler after the diodes are secured therein. The method also includes the step of reflow soldering the rectifier in a solder oven for final assembly. A connector housing is inserted over the terminal connector and includes a connection for receiving a wiring harness and establishing electrical contact with the terminal connector. The method also includes the step of securing a terminal connector to the insulated conductor substrate and having a terminal for connecting to the wiring harness.